Switching the WAM Between Internal & External Control

The WAM is controlled from a real-time operating system (RTOS) and a set control rate (usually 500 Hz, but configurable up to 1 kHz depending on the hardware configuration). Newer WAMs (types D and E) include a built-in PC-104 embedded computer in their base, which is loaded with a suitable RTOS to control the WAM at up to 750 Hz. Customers can communicate with this internal PC using Ethernet for asynchronous control. Barrett also sells modern Linux desktop PCs pre-loaded with a suitable RTOS (most recently, RTAI or Xenomai under Linux), which communicates directly with the WAM's Puck motor controllers to control the WAM.

Here is a summary of the pros and cons of using each option:

Internal PC104	External PC
WAM is entirely self-contained	External desktop PC required
No expansion options	2 PCI expansion slots (or more in custom installation)
750 Hz maximum control rate	1 kHz maximum control rate
Command-line access only	Full desktop PC; easier to develop on

Switching Modes

Newer WAMs which include an embedded internal PC (types D and E) include internal switches to select which mode is to be used. Warning: Never alter the switches while the system is on; doing so may do irreparably damage the safety board. Always switch off the WAM's power supply first!

AE Safety Board (WAM Type E)

The necessary switches are located on the safety board. Un-clip the four outer cover clips (two on each side) and remove the single screw on the top-left of the back cover with a 4mm hex wrench. There are 4 switches located along the side of the board (see attachment:safetyboard_ae_switches.jpg); switches C and D control the CAN routing. Use the following table to select the correct positions:

	Switch C	Switch D
Internal (PC-104)	IN	IN
External (Desktop PC)	OUT	OUT

Warning: Never alter the switches while the system is on; doing so may do irreparably damage the safety board. Always switch off the WAM's power supply first!

Note: It is possible to control two WAMs from one PC-104 internal PC. You will need a special cable to connect the WAMs via the external CAN connectors on the back of each system (contact Barrett for information). Configure the slave system for External control. Configure the master system for Internal control. In addition, you will need to toggle an additional switch on the master system underneath the safety board cover; switch E is normally OUT -- on the master system, you will need to switch this to IN. See attachment:safetyboard_ae_under_switches.jpg.

NOTE: The above is not entirely correct. Switch E does not get stuffed consistently in the same orientation. We will need to include documentation to show the user which way is ON (connected, for special case) and which is OFF (disconnected, default).

AD Safety Board (WAM Type D)

Coming Soon ... (contact support@… for questions)